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AUXINS:  Darwin performed some experiments on canary grass. In his experiments, when the coleoptile of grass was unilaterally illuminated, it curved towards the source of light. The experiments done by him confirms some interations  between the tip and light and light resulting in curvature of tip.     Went removed the tip of avena coleoptile and placed it on agar-agar block for a measured length of time and it produces a positive curvature. He named this substance as Auxin. Isolation of Auxin Kosland Hargen-Smith isolated Auxin-A from human urine. Kogl, Erxlaben and Hargen- smith isolated Auxin-B from corn germ oil. It was chemically identified as Indole-3 Acetic Acid(IAA). Biosynthesis of Auxins Thimann 1935 observed the fungus Rhizopus Suinus can convert the amino acid Tryptophan into IAA. Transport: Auxins occurs in the meristems. It is transported polarly and movement is basipetal. Physiological effects: Induces cell elongation Plays an importan

Growth in plants: Growth is irreversible and permenant increase in size of cell or tissue or organ or entire plant body. It is always accompained by metabolic associated reactions. Growth in plants is indeterminate and grows till death due to the activity of meristems in plants. Growth can be measured by increase in protoplasmic content, fresh weight, dry weight, length, area, volume and number of cells.  Phases of growth: In plants growtg and development each cell undergoes three phases. 1. Meristematic phase:       In this phase meristematic cells divides continuously. The cells are active and this phase is also called as Cell-division Phase. 2. Elongation phase:        The cells which are formed in meristematic phase becomes enlarged in thier size and forms vacoules at the centre of the cell. 3. Maturation phase:          The cells are matured and differentiated into tissues to perform special functions like transportation food, water, minerals, etc,..